1. Field of the Invention
The present invention relates to a diaphragm, a diaphragm valve, and a method of manufacturing a diaphragm.
2. Description of the Related Art
In a semiconductor manufacturing gas process or the like in which highly corrosive gas is used, a diaphragm valve that functions as an open/close valve for the corrosive gas is required to have high corrosion resistance. Therefore, conventionally, as a diaphragm of high performance used in a semiconductor manufacturing gas process or the like, a metal diaphragm made of a superalloy of a cobalt group, a nickel group, etc. is used.
Further, a diaphragm valve used for the above-mentioned application is required to have strength that enables baking in a low to high temperature range and withstands a low pressure to a high pressure exceeding 150 kg/cm2. Further, because the metal diaphragm is used repeatedly at a high frequency as an open/close valve for corrosive gas, the metal diaphragm is required to have durability under such a severe use environment.
In order to satisfy such requirements, a metal diaphragm or diaphragm valve excellent in characteristics such as corrosion resistance and durability has been developed actively (see, for example, Japanese Patent Application Laid-open No. 08-4918).
In recent years, along with the enlargement of a system along with the enlargement of a silicon wafer, a liquid crystal panel, etc. and the streamlining of a semiconductor manufacturing facility, there is a tendency that a flow rate (CV value) of gas flowing through the diaphragm valve is increased. The diaphragm valve opens/closes a valve set in a flow path of gas by deforming a swelling portion of a dome-shaped metal diaphragm, to thereby function as an open/close valve for gas. Therefore, in order to increase a flow rate (Cv value) of gas, it is necessary to increase a displacement amount (deformation amount) of the metal diaphragm at the time of open/close of the valve and to increase the amount of gas flowing through the diaphragm valve.
However, when the displacement amount of the metal diaphragm is increased, the stress applied to the metal diaphragm is increased, which reduces the durability of the diaphragm valve. Therefore, it has been difficult to increase the displacement amount of the metal diaphragm while maintaining durability.